This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A054261 #30 May 10 2019 09:18:42 %S A054261 2,23,235,2357,112357,113257,1131725,113171925,1131719235, %T A054261 113171923295,113171923295,1131719237295,11317237294195, %U A054261 1131723294194375,113172329419437475,1131723294194347537,113172329419434753759 %N A054261 Smallest number that contains the first n primes as substrings. %C A054261 The version that allows substrings to go from left to right or right to left is A240959. - _Dmitry Kamenetsky_, Oct 07 2015 %H A054261 Anders Kaseorg, <a href="/A054261/b054261.txt">Table of n, a(n) for n = 1..510</a> %H A054261 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_408.htm">Puzzle 408. First primes embedded in the smallest number</a> %Y A054261 Cf. A054260, A035239, A240959. %K A054261 nonn,base,nice %O A054261 1,1 %A A054261 _Patrick De Geest_, Feb 15 2000 %E A054261 More terms from _Naohiro Nomoto_, Jul 26 2001